2015 High Miler

Im at 206,000 and just added headers and a tune. Runs like a top, today anyway. got 21.3 on the highway at 65-70 usually running 80-85 and its at 16-17 MPG. Change the oil and you should be good.

Old thread but this looks like a good option.to keep out rodents and debris:

Yes I have A full set I’d sell.

2015 Sierra SLT 5.3 206,000 miles Im having an ongoing issue with exhaust smell in the cab through my AC, especially when sitting in traffic or at a light. At 122,****** miles, I had my trans replaced through the dealer under partial warranty. A few thousand miles later is when the smell started and I took it back. They told me one of the exhaust connections they had removed for the swap was leaking and they fixed it. That lasted about 15-20,000 miles. It started leaking again but COVID hit and I was not driving as much so I didn't take it back until late last year and at that time they gave me a laundry list of "exhaust issues" that was causing this smell. Cracked manifold, cracked y pipe, cats needed changed, etc to the tune of $3800. AT that point, I knew I could find a better way so nothing was done. I felt like they didn't know what was wrong with it honestly. All of that lead to my recent header and ORY pipe install, plus a new tune, but last night while driving it any real distance for the first time, I am still getting an exhaust gas smell through the AC when stopped at a light or what ever. In the past, if I remembered to turn the AC, I would not get the smell and that is how I knew it was coming in through the AC air intake. But summer is here and I will def need AC in Texas. Ive checked the new pipes and do not see any witness of leaks but I've put less than 150 miles on it at this point. Has anyone else seen this or had it happen to them? I can live with it but the family isnt a fan of the smell... Thanks

Yes for sure on both points! When they couldn't determine what exactly it was that was wrong with it and just wanted to do a cam swap, I knew I needed to take it elsewhere.

Embarrassing... for me and the shop. One coil was unplugged... not the plug wire but the coil itself. Getting the truck tuned at the current shop. Trusting their experience a little more at this point.

Locally, so far I've been quoted $3000 and done with engine in the truck to $4000 for pulling the engine and taking it down to the short block to complete the updates. New cam with AFM delete and retune. I'm leaning more to the more expensive option due the experience level of the shop vs the less expensive one.

I don’t think they did it. No blame placed. I’m trailering it so no more driving for sure. Thanks for all the comments so far. I’ll post the diagnosis.

Click here to listen Im taking it to a more experienced shop tomorrow for another opinion.

Yes they swapped out to another set of new plugs and replaced the wires back to the original. Number 7 is miss-firing.

2015 5.3 205,000 miles. Have not had any issues engine wise, except it’s had a manifold gasket leak for about 6-7 months. I decided to replace with headers and ory pipe since I’m there. Also replaced spark plugs and new wires. Engine now has a miss so bad they can’t tune it... shop owner thinks it is a collapsed lifter. Is there anything they could have done to cause this to kiss so bad they can’t tune it? They have even changed plugs and replaced the old wires to rule out bad ones. No luck. im taking it to get a second opinion. I’m going to have to drive it 40 miles round trip like this. Am I risking more damage if it is a lifter? I just don’t know if I trust this shop right now. They say they have experience but I’m not feeling it. It was a simple header change but now it’s def something else. I’m just looking for ideas. I was interested in doing a cam and AFM delete at some point but def not today, or even this year.

Old post

Not sure asking here has had any benefit as there are opposing views in both directions. LOL what else could I excect by asking a generic question on an internet forum! I do appreciate the feed back. Looking at a couple more trucks this weekend so i may be back with more questions....

OTR, this is a def option for me. I am not driving as much as I once was pre-COVID so keeping it and doing a complete tune up/upgrade may been smart. I used to drive 5-6000 a month but now I am at 25-3000. This whole process started because I started adding up the tune-up/maintenance/repair costs and I thought that would be a great down payment on something newer with less miles, and a moonroof with 22's. LOL To your point about values, Im seeing 100,000+ miles for sale at 31,000! 8-/

Yes, I work very hard for the money, but I have to be cognizant of cost. The 19+ are $10-15,000 more and I have a daughter getting married next year (surprise) plus 3 other daughters. LOL I may just hang on to what I have for the time being. My 15 has the GM clunk in the shift at times but I have gotten used to it I guess. I also have an for intune 2 and have dialed in the shift fairly well. To the Chevy shake and other issues, it always concerns me buying an older low mileage vehicle like what I am looking at. Did they just not drive much and trade every 3-4 years or was it a buyback or was there something wrong with it and they just got rid of it...I would asume they would have to note its a buyback but that doesn't mean they do. The used 19's are not are not that far off from a new 2021s. Used 19's are $55-60,000. New 21's are $60-68,000. Used 18's are $43-47,000 and not many at 43. Most are $45-47. These are all Denali's.

I found an 18 2wd with 6.2 and 8 speed that im going to look at this weekend. Its 2 hours away so I hope It works out. Anything specific to feel for with the 8 speed? Ive read some but making sure I am not missing anything.

OLM on my 15 is 7500 regardless of how hard I drive it. Tires are Michelin and are rated @ 70000 but usually get 50000 miles. Still on factory plugs at 200000 and get 18-19 mpg on highway at 75. (I dont drive 75 often though.). Also not saying that is right but it is where I am at with my truck. Also, I use full synthetic and Wix or ac Delco filters and go 10000 on changes. I used To have the oil tested and 10000 was always good so I have Not tested in a while. Brakes made it to 165000 but I rarely pull a trailer and my daily drive was 225 miles, mostly highway. jusy my experience.

I found a 2019 2wd with the 5.3 but it has the 8 speed as well. Is there an issue with the ‘19 8 speeds as well?

Great replies. . Thank you. ive put 200,000 on it and as I said, I love it. Ive considered keeping it. It’s very comfortable and i make a lot of long road trips 2-4 hours and don’t want to lose that. With more features and just less miles in general, a new used truck seems to be a wise choice. I have also considered keeping what I have and adding some performance pieces. Been a great truck other than having trans replaced at 120,000. Decisions decisions.

I’m shopping for a new used truck. I def want the 6.2 so I am looking at Denali 1500’s. I have a ‘15 and have loved it so I’m really okay with the 18 body style. But I’ve seen a few 19’s that I like as well. They are usually about $7-10,000 more though. I’m wondering if anyone has any feedback that has had both and if there is anything that makes one a better choice than the other. I’m torn on which one to get so just looking for some experiences. thanks

As my name indicate, I have a 15 Sierra with 200,000+ miles. Ive replaced the pads and had rotors turned 30,000 miles ago. Lately at slow speeds, like a drive through or super slow traffic, I have noticed the brakes grabbing. I believe I have narrowed it down to the fronts but not 100% sure. . At highway or reg speeds, I dont notice it but at slow speeds it’s very “grabby” . Ive had the brakes recall service performed.as well. Anyone experienced this before and have a diagnosis? thanks

Thanks for the opinion on the cats. it’s a daily driver and I was Thinking the cats would keep it legal and tone down the sounds “some”. I’m not locked on having them though.

I have 2015 Sierra stock (for now) 5.3 w 200,000 miles. I want upgrade to headers and hi flow cats to replace a cracked manifold. I’m seeing a range in prices from $299 for just headers to $1800 for a complete system. I was quoted $950 from a local shop installed, w cats and o2 extenders. I’m not really thinking I NEED stainless due to age of truck and the mostly mild environment I live in. But I don’t want it to come apart and need repairs often either. Im looking for a good value for performance/durability system. For those of you with experience, can you point me in a good direction as far as what’s what? for the record, I tried a search but it was in conclusive. Thanks

197,****** same plugs same wires same coils. signed ??? I have been searching for good replacements for no other reason than I feel guilty.

197,******. No catch can. Runs great. I did have to replace the trans at 122,000 but nothing else. Knock on wood...